Emmanuel Macron, former French economy minister and head of the political movement "En Marche" or "Forward", delivers a speech during a meeting in Paris, France, November 5, 2016. REUTERS/Jacky Naegelen - RTX2S23U

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By Emmanuel Jarry and Sophie Louet

PARIS (Reuters) - Former economy minister Emmanuel Macron will announce on Wednesday a run for the French presidency, a source close to him said, a long-awaited move that could disrupt other campaigns on both the left and the right.

The 38-year-old former investment banker quit his job as economy minister earlier this year and has set up his own political movement called "En Marche" (Forward).

"He has made up his mind and the decision was taken a long time ago," the source said.

Despite his past role in Socialist President Francois Hollande's government and as an adviser to him before that, Macron is not a member of the Socialist Party.

He is also not an elected politician, and commentators say his lack of a party apparatus makes him an unlikely winner.

However, as one of France's most popular politicians, his policies take aim at the center ground, which is also the target of Alain Juppe, the pollsters' current favorite to become president in the two-round election next April and May.

Macron's widely-expected intervention comes just days before the first round of the primaries of the Les Republicains party and its center-right allies on Sunday, and the timing was not lost on one of Juppe's supporters in parliament, Benoist Apparu.

"He said, broadly - 'I am going to do politics differently, outside of political clans and parties'" Apparu said on BFM TV. "And then the first thing he does is a purely political, calculated, electoral move, telling himself, 'I will try and falsify ... the result of the center-right primary."

Juppe's main rival to win that contest is former president Nicolas Sarkozy, who has positioned himself to ex-prime minister Juppe's right in an attempt to capture voters worried about immigration and security.

Opinion polls in recent months have shown that whoever wins the Le Republicains ticket will face, and beat, Marine Le Pen, the leader of the far-right National Front, in the second round of the election proper next May.

But the battle is a complex one.

New doubts have emerged about the accuracy of opinion polls since Britons voted unexpectedly to quit the European Union and Donald Trump won the U.S. presidency, particularly with regard to the populist voters to whom Sarkozy and Le Pen have appealed.

In addition, left-wing voters are widely expected to gatecrash the Les Republicains primaries, voting in large numbers for Juppe to avoid a Sarkozy-Le Pen choice in next year's election proper.

French voters can cast ballots in the primaries whether they are party members or not. Apparu's objection is rooted in the expectation that some who would have voted for Juppe in the primaries might hold off if Macron is going to run.

Macron aides have said he will not take part in January's Socialist primaries, but he could make further inroads on those voters who still favor the deeply unpopular Hollande for a second term, or who plan to vote for Prime Minister Manuel Valls should Hollande decide not to run and Valls take his place.

That would further split the vote in an already crowded Socialist primaries field.

An October poll published by Odoxa put Macron at the top of a list of potential presidents from the left, with 49 percent considering him a good head of state. Valls came second on 42 percent while Hollande was out of the running on 13 percent, behind several others.

Among Socialist voters, Valls came first on 70 percent with Macron in second place on 50 percent.

(Reporting by Emmanuel Jarry; Writing by John Irish and Andrew Callus; Editing by Tom Heneghan)